Epilobium cupreum Lange; E. foucaudianum H. Léveillé; E. steckerianum Fernald

Leaves not coriaceous, petiole 3–7 mm proximally; cauline blade 1.5–5.5 × 0.7–2.9 cm. Flowers: sepals sometimes red-tipped, 2–4.5 × 1–2.2 mm; petals usually rose-purple to light pink, rarely white, 3–9 × 2–5.5 mm. Capsules 40–65 mm. Seeds 0.9–1.2 × 0.3–0.5 mm, surfaces distinctly papillose. 2n = 36.

Flowering (May–)Jun–Aug. Banks of montane to alpine streams and lakes, open tussock meadows, willow swales, gravelly ridges, stabilized scree slopes, road­side ditches; 50–3700 m; Greenland; Alta., B.C., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, Ont., Que., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Maine, Mont., Nev., N.H., N.Mex., N.Y., Oreg., S.Dak., Utah, Wash., Wyo.; n Eurasia.

Subspecies hornemannii is one of the more com­mon and widely distributed members of the Alpinae alliance and carries the CC chromosomal arrangement. It grows from near sea level in the north (Alaska, Northwest Territories) to high alpine (to 3700 m) in the southern Rockies and Sierra Nevada; it also occurs in northern Europe, subarctic and Russian Far East, and Japan. In Nunuvut, it is found only on Charlton Island in James Bay. It often grows sympatrically with E. ciliatum and Epilobium saximontanum (both AA arrangement); occasional hybrids are found, but they often have much reduced seed fertility, probably due to chromosomal irregularities.

Subspecies hornemannii occurs occasionally in spring pools, forming distinctive dense floating mats of ascending stems. Specimens growing in very moist habitats often have pale, thin epigeal stolons with scales, rather than typical leafy soboles.